IPs on a VPS are added from the hardware node on which your VPS is created. You need to contact your hosting company for that.

You will have to get your name servers registered from your domain registrar end and have to assign them any of two IPs you have received. You can then setup the name servers on your server from WHM >> Basic cPanel/WHM Setup option. You can also refer below doc:http://cpanel.net/docs/whm/

Once the name servers start pointing to your server, you can then assign to your domains.